Multiturn sensor arrangement and readout

ABSTRACT

A system includes a multiturn counter that can store a magnetic state associated with a number of accumulated turns of a magnetic field. The multiturn counter includes a plurality of magnetoresistive elements electrically coupled in series with each other. A matrix of electrical connections is arranged to connect magnetoresistive elements of the plurality of magnetoresistive elements to other magnetoresistive elements of the plurality of magnetoresistive elements.

RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.15/064,544, filed Mar. 8, 2016, the disclosure of which is herebyincorporated by reference in its entirety herein.

TECHNOLOGICAL FIELD

This application relates to sensors, and more particularly, to multiturnsensors such as giant magnetoresistance multiturn sensors.

BACKGROUND

A multiturn counter can keep track of how many times an apparatus orelement thereof has been turned. This can be implemented using anelectromagnetic system. Electromagnetic multiturn sensors can includeelectrical multiturn sensors, magnetic multiturn sensors, and multiturnsensors that use both electrical and magnetic principles. An example ofelectromagnetic multiturn sensor includes a giant magnetoresistance(GMR) sensor.

Multiturn counters have a variety of uses. Electronic implementations ofmultiturn counters can translate a physical position or motion into anelectromagnetic representation suitable for processing. For example,drive-by-wire cars can use a multiturn counter to track how many times asteering wheel has been turned. This, for example, allows a vehiclecontrol system to differentiate between when a steering wheel is at 45degrees or 405 degrees, despite the steering wheel being in the sameposition at both angles.

Multiturn sensors can be implemented using multiple Wheatstone bridgesas sensing circuits, multiple sensor outputs, and numerous internalinterconnections to detect voltages. These multiturn sensors can includea relatively large number of more sensors and sensor outputs as thenumber of countable turns increases.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

One aspect of this disclosure is a system that includes a multiturncounter configured to store a magnetic state associated with a number ofaccumulated turns of a magnetic field. The multiturn counter isconfigured to count at least two turns, and the multiturn counterincludes a plurality of magnetoresistive elements electrically coupledin series with each other, the plurality of magnetoresistive elementscomprising at least eight magnetoresistive elements. The multiturncounter also includes a matrix of electrical connections arranged toelectrically connect magnetoresistive elements of the plurality ofmagnetoresistive elements to other magnetoresistive elements of theplurality of magnetoresistive elements, the matrix being at least threeby three.

In the system, the plurality of magnetoresistive elements can be part ofa magnetic strip that is physically laid out in the shape of a spiral.

The system can also include a sensing circuit configured to sense asequence of properties of the plurality of magnetoresistive elements andalso configured to provide an output indicative of the number ofaccumulated turns of the magnetic field, and a driving circuitconfigured to apply combinations of voltages or currents to the matrixof electrical connections in a sequence, thereby enabling the sensingcircuit to sense the sequence of properties.

The a sensing circuit can include a first sample and hold circuitconfigured to sample at a first time, a second sample and hold circuitconfigured to sample at a second time that is different from the firsttime, and a comparator configured to compare an output of the firstsample and hold circuit with an output of the second sample and holdcircuit.

The system can also include a magnet positioned within a distance closeenough to cause the domain wall generator to change domain walls in theplurality of magnetoresistive elements, thereby changing a resistance ofat least one of the magnetically magnetoresistive elements in responseto the magnet rotating 180 degrees.

In the system, the multiturn counter can further include a domain wallgenerator coupled to one end of the plurality of magnetoresistiveelements, the domain wall generator configured to generate a domain wallat a corner in the magnetic strip, thereby causing a magnetoresistiveelement to change resistances.

In the system, the multiturn counter can be configured to count N turns.The system can also include a number of sensing circuits, the numberbeing less than 2 times N and a plurality of switches is configured toelectrically couple an individual magnetoresistive element to anindividual sensing circuit of the number of sensing circuits.

In the system, the spiral has can have N magnetoresistive elements,where N is greater than or equal to 8. The spiral can have R physicalconnections to rows of electrical connections of the matrix ofelectrical connections. The spiral can have C physical connections tocolumns of electrical connections of the matrix of electricalconnections. The following equations can be satisfied: N<(R+1)*(C+1);and N>(R−1)*(C−1). Both C and R can be 3 or greater.

Another aspect of this disclosure is directed to a giantmagnetoresistance (GMR) sensor. The GMR sensor includes a magnetic stripcomprising magnetoresistive elements electrically coupled in series witheach other, the magnetic strip having a spiral shaped layout, and eachof the magnetoresistive elements of the magnetic strip having at leasttwo states associated with different resistances. The GMR sensor alsoincludes a matrix of electrical connections electrically coupled to aplurality of nodes along the magnetic strip, the matrix being at leasttwo by two and comprising rows of electrical connections and columns ofelectrical connections. The GMR sensor also includes a sensing circuitelectrically coupled to the matrix of electrical connections, thesensing circuit configured to determine a state of a selectedmagnetoresistive element of the plurality of magnetoresistive elements.

The GMR sensor can also include a driving circuit configured tosequentially supply power through different combinations of electricalconnections in the matrix of electrical connections, and provide asequence of electromagnetic readings from which a cumulative turn stateis determinable.

The driving circuit of the GMR sensor can also include row switchesconfigured to selectively electrically couple a first signal referenceto a selected row of the rows of electrical connections. The drivingcircuit of the GMR sensor can also include column switches configured toselectively electrically couple a second signal reference to a selectedcolumn of the columns of electrical connections. The column switches canbe configured to selectively electrically couple the sensing circuit tothe selected column of the columns of electrical connections.

In the GMR sensor, the sequence of combinations can include combinationsthat cause power to be provided to a sequence of individualmagnetoresistive elements.

The GMR sensor can also include an amplifier configured to output ananalog signal, an analog to digital converter configured to convert theanalog signal into a digital signal, and a digital comparator configuredto compare a first digital value of the digital signal with a seconddigital value.

In the GMR sensor, the spiral can have N resistive segments and 2N+2 orfewer than physical connections with the matrix.

Another aspect of this disclosure is directed to a method for reading astate of a giant magnetoresistance (GMR) sensor. The method includespowering a first sequence of rows in a matrix, the rows being coupled toa strip of a plurality of magnetoresistive elements. The method includespowering a second sequence of columns in a matrix, the columns beingcoupled to the strip of the plurality of magnetoresistive elements. Themethod includes sensing a sequence of electromagnetic properties ofindividual magnetoresistive elements of the plurality ofmagnetoresistive elements. The strip of magnetoresistive elements isphysically laid out as a spiral. The strip includes strip corners. Thestrip also includes strip sides that have a variable resistance. Theplurality of magnetoresistive elements includes the sides.

In the method, powering the first sequence of rows in the matrix andpowering the second sequence of columns in the matrix can be performedsuch that the guarding principle enables the sensing of theelectromagnetic properties of the individual magnetoresistive elementsof the plurality of magnetoresistive elements.

In the method, powering the first sequence can include providing acurrent source to a first row while grounding a second row and alsoinclude providing a current source to the second row while grounding thefirst row. Powering the second sequence can include providing thecurrent source to a first column and subsequently providing the currentsource to a second column.

The method can also include sampling and holding a first voltage acrossa first magnetoresistive element of the plurality of magnetoresistiveelements. The method can also include sampling and holding a secondvoltage across a second magnetoresistive element of the plurality ofmagnetoresistive elements. The method can also include comparing thefirst voltage to the second voltage.

The method can also include generating a domain wall at a corner in thestrip

The method can also include determining a number of turns of a magneticfield permeating a domain wall generator with 180 degree accuracy, thedetermining comprising decoding a series of sensed voltages.

For purposes of summarizing the disclosure, certain aspects, advantages,and novel features of the innovations have been described herein. It isto be understood that not necessarily all such advantages can beachieved in accordance with any particular embodiment. Thus, theinnovations described herein can be embodied or carried out in a mannerthat achieves or optimizes one advantage or group of advantages astaught herein without necessarily achieving other advantages as can betaught or suggested herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example magnetic strip layout representation with acorresponding circuit schematic representation.

FIG. 2 shows an example magnetic strip layout representation withexplanatory symbols.

FIG. 3 shows an example schematic diagram of a multiturn counter with amatrix of interconnects to a series of magnetoresistive elementsaccording to an embodiment.

FIG. 4 shows an example layout view of the matrix from FIG. 3electrically connected to the magnetoresistive elements of the magneticstrip from FIG. 1 according to an embodiment.

FIG. 5 shows a schematic diagram of a matrix electrically connected to aseries of magnetoresistive elements for a 46 turn counter according toan embodiment.

FIG. 6 shows an example schematic of an electronic system that includesa driving and sensing circuit electrically connected through a matrix ofinterconnects to a series of magnetoresistive elements according to anembodiment.

FIG. 7 shows an example schematic of a driving and sensing circuitelectrically connected through a matrix of interconnects to a series ofmagnetoresistive elements according to an embodiment.

FIG. 8 shows an example multiturn counter system according to anembodiment.

FIGS. 9-18 show an example of progressive turn states of an example 2turn counter as a magnetic field rotates in accordance with anembodiment.

FIG. 10 shows the example 2 turn counter of FIG. 9 in a starting stateat 0 degrees.

FIG. 11 shows the example 2 turn counter of FIG. 9 in a state where themagnetic field has rotated clockwise 90 degrees.

FIG. 12 shows the example 2 turn counter of FIG. 9 in a state where themagnetic field has rotated clockwise 180 degrees.

FIG. 13 shows the example 2 turn counter of FIG. 9 in a state where themagnetic field has rotated clockwise 270 degrees.

FIG. 14 shows the example 2 turn counter of FIG. 9 in a state where themagnetic field has rotated clockwise 360 degrees.

FIG. 15 shows the example 2 turn counter of FIG. 9 in a state where themagnetic field has rotated clockwise 450 degrees.

FIG. 16 shows the example 2 turn counter of FIG. 9 in a state where themagnetic field has rotated clockwise 540 degrees.

FIG. 17 shows the example 2 turn counter of FIG. 9 in a state where themagnetic field has rotated clockwise 630 degrees.

FIG. 18 shows the example 2 turn counter of FIG. 9 in a state where themagnetic field has rotated clockwise 720 degrees.

FIGS. 19-20 show an example of progressively reversing turn statesfollowing the turn state of FIG. 15 in accordance with an embodiment.

FIG. 19 shows the example 2 turn counter of FIG. 15 in a state where themagnetic field has rotated counterclockwise 90 degrees to have anaccumulated rotation of 360 degrees.

FIG. 20 shows the example 2 turn counter of FIG. 19 in a state where themagnetic field has rotated counterclockwise 90 degrees to have anaccumulated rotation of 270 degrees.

FIG. 21 shows an example method for reading a state of a giantmagnetoresistance sensor according to an embodiment.

FIG. 22 shows an example method for making a multiturn sensor accordingto an embodiment.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following detailed description of certain embodiments presentsvarious descriptions of specific embodiments. However, the innovationsdescribed herein can be embodied in a multitude of different ways, forexample, as defined and covered by the claims. In this description,reference is made to the drawings where like reference numerals canindicate identical or functionally similar elements. It will beunderstood that elements illustrated in the figures are not necessarilydrawn to scale. Moreover, it will be understood that certain embodimentscan include more elements than illustrated in a drawing and/or a subsetof the elements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

As discussed above, multiturn sensors can be implemented using multipleWheatstone bridges as sensing circuits, multiple sensor outputs, andnumerous internal interconnections to detect voltages. These multiturnsensors include more sensors, more sensor outputs, and more complicatedinternal connections as the number of countable turns increases. Theadditional outputs and sensors can increase linearly with the number ofcountable turns. The Wheatstone bridges, sensor outputs, and internalinterconnections can consume a relatively large amount of die area. Themultiturn sensors that use Wheatstone bridges can have twice as manysensor outputs as the number of turns that the multiturn sensor isdesigned to count. For example, a 16 turn sensor can require 32 sensoroutputs. As a result, multiturn sensors designed to count many turns canrequire a large die area for the Wheatstone bridge circuits and outputs.In multiturn sensors that use multiple voltage supplies and tie outputstogether in an effort to reduce die area, the output signal can bereduced significantly. Reduced output signals can involve more sensitivesignal detectors and other circuitry.

In some embodiments, a multiturn counter is physically laid out as aspiral track coupled to a domain wall generator. A matrix of connectionscreates relatively short connections between different segments of thespiral track. A driving circuit and a sensing circuit are coupled torows and columns of the matrix. A combination of switches coupled to therows and columns of the matrix are opened and closed in a sequence sothat individual resistances can be sensed. The sequence of sensedresistances can be compared and/or decoded to determine and accumulatedturn state.

In some embodiments, a magnetic strip having a magnetic anisotropy isphysically laid out in the shape of a spiral. A domain wall generatorcoupled to one end of the magnetic strip is configured to generate andtransport one or more domain walls through the magnetic strip accordingto the orientation of a rotating magnetic field. A matrix of electricalconnections, such as a logical matrix of electrical connections, can bephysically implemented with the spiral shaped magnetic strip. Thephysical layout of the electrical connections can look different from aschematic row/column representation of the matrix. A driving circuit canactivate (e.g., provide a voltage and/or current to) a portion of thespiral and a sensing circuit can make an electromagnetic readingassociated with the portion of the spiral. As such, the sensing circuitcan sense a resistance of an isolated magnetoresistive element of themagnetic strip. A control circuit can control a sequence in whichdifferent parts of the spiral can be powered and sensed by a sensingcircuit. For instance, the control circuit can control switches toselect a particular magnetoresistive element of the spiral for which thesensing circuit can sense a value indicative of resistance. The sensingcircuit can make a sequence of electrical readings of the various partsof the spiral associated with magnetic states of the various parts ofthe spiral. In some instances, the sensing circuit can perform acomparison of the electromagnetic readings. The output of the sensingcircuit can be decoded to determine an accumulated turn state of themagnetoresistive elements of the magnetic strip.

In some embodiments, the use of a matrix of electrical connections canreduce and/or minimize the electrical connections to the spiral. In someembodiments, fewer sensors are used to read out the state of themultiturn counter, thereby consuming less physical die area and reducingfabrication costs. In some embodiments, a comparator circuit can provideaccurate readings over a relatively large range of temperatures.

The various embodiments of multiturn counters described in thisdisclosure can have one or more the following advantages, among others.The multiturn sensor can have fewer outputs compared to other designssuch as designs that use Wheatstone bridges. The multiturn sensor candetect an accumulated number of turns with 180 degree resolution. Themultiturn sensor can include a matrix that allows for selecting andoutputting individual signals without causing signal reduction andwithout needing to combine signals. The multiturn sensor can use lesssensitive sensors (e.g., voltmeters, ammeters, ohmmeters, or samplingcircuits), a sensing circuit can measure values for individualmagnetoresistive elements, fewer sensing circuits can be used, and feweror no Wheatstone bridge circuits can be used. The multiturn sensor canallow for lower costs of production, smaller physical size, easierfabrication, and fewer interconnections. The multiturn sensor canfunction accurately over a relatively large temperature range. Themultiturn sensor can have fewer or no voltmeters for readout and alsohave fewer parts. The multiturn sensor can have nonvolatile memory thatcan be written to even when not powered. The multiturn sensor can counta greater number of turns, have a higher turn to sensor ratio, have ahigher turn to connections ratio, and have a higher turn tomagnetoresistive element ratio. Wheatstone bridge circuits, sensors, andinterconnections can take up die area and create complexity, so theiruses can be minimized, and Wheatstone bridges can be avoided altogether.Furthermore, each magnetoresistive element can be individually measuredby relatively less expensive sensing circuits, while at the same time,the number of sensing circuits and sensor outputs can remain relativelylow (e.g., 1 or 2) even for large numbers of magnetoresistive elements.

FIG. 1 shows an example magnetic strip layout 100 with a correspondingcircuit schematic representation 150. FIG. 1 shows a magnetic strip 101having corners 105 and segments 103 a-103 n forming magnetoresistiveelements R1-R14 arranged in series with each other, and a domain wallgenerator 107. The magnetoresistive elements can act as variableresistors that change resistances in response to a magnetic alignmentstate. The magnetic strip 101 illustrated in FIG. 1 can be implement ina multiturn counter that can count at least 3 turns.

The magnetic strip 101 can be a giant magnetoresistance track that isphysically laid out in the shape of a spiral. As illustrated in FIG. 1,such a spiral shaped magnetic strip 101 can have rounded corners 105 andsegments 103 a-103 n. The magnetic strip 101 can have a magneticanisotropy, such as a high anisotropy, based on the material and crosssectional dimensions of the magnetic strip 101. The magnetic strip 101can store magnetic energy. A domain wall generator (DWG) 107 is coupledto one end of the magnetic strip 101. The DWG 107 can have a magneticanisotropy, such as a low anisotropy. The domain wall generator cangenerate domain walls in response to rotations in a magnetic field. Thedomain walls can be injected to the magnetic strip 101.

The segments 103 a-103 n of the magnetic strip 101 are shown as straightsides of the magnetic strip 101 in the example of FIG. 1. The segments103 a-103 n can have a variable resistance based on the magnetic domainof the segment. As the magnetic domain of a segment changes, theresistance of that segment can change. Accordingly, the segments 103a-103 n can operate as magnetoresistive elements, also referred to asvariable resistors R1-R14 herein. The magnetoresistive elements R1-R14can also function as nonvolatile, magnetic memory that can bemagnetically written and electrically read. The magnetoresistiveelements R1-R14, as laid out in the spiral shaped magnetic strip 101,are coupled in series with each other. Corresponding circuit schematicrepresentation 150 shows segments 103 a-103 n depicted as correspondingmagnetoresistive elements R1-R14 connected in series.

FIG. 2 shows an example magnetic strip layout representation 200 withexplanatory symbols. The magnetic strip 101 with magnetoresistiveelement segments equivalents R1-R14 of FIG. 1 is shown, along with DWG107, an external magnetic field 201, an arrow 203 indicating a rotationof the external magnetic field 201, and a domain wall 213. Domainorientations 205, 207, 209, and 211 indicate an orientation of a domaininside of a segment of a magnetic strip.

The DWG 107 can be affected by the external magnetic field 201. As theexternal magnetic field 201 rotates as indicated by arrow 203, the DWG107 can inject domain walls 213 through the magnetic strip 101. Thedomain wall 213 can propagate through the segments as the domainorientations 205, 207, 209, and 211 change. Although FIG. 2 and FIG.9-20 show the external magnetic field 201 at perpendicular positions forclarity, the magnetic field can be pointed at any angle, such as a 45degree angle toward the spiral corners.

The resistivity of segments of the magnetic strip 101 can be affected bythe domain orientation within a magnetic strip segment. Each segment'sdomain orientation can cause that segment to have a high resistance (“H”or “HR”) or a low resistance (“L” or “LR”) depending on the orientationof the segment. Vertically illustrated magnetic strip segments having adomain orientation 205 have a higher resistivity than vertical magneticstrip segments having a domain orientation 207, which have a lowresistivity. Horizontally illustrated magnetic strip segments having adomain orientation 213 have a higher resistivity than horizontalmagnetic strip segments having a domain orientation 211, which have alow resistivity. The magnetic strip segments with domain orientations205 and 213 can have comparable resistances. Similarly, the magneticstrip segments with domain orientations 207 and 211 can have comparableresistances.

The actual resistances can vary between different segments of themagnetic strip 101. For example, with reference to FIG. 1, segment 103 bat a HR magnetic orientation can have a smaller resistance than segment103 c at a HR magnetic orientation because segment 103 c is slightlylonger than segment 103 b. This difference can be exacerbated betweenthe first segment and the last segment in relatively large spirals. Aspiral shaped magnetic strip 101 can be relatively compact to reduceand/or minimize die area. A relatively small, compact spiral shapedmagnetic strip 101 having incrementally larger segments can avoid theproblem where a longer magnetic strip at low resistivity has a higherresistance than a shorter magnetic strip at a high resistivity. In someembodiments, the difference in resistivity, and not the length of thesegments, is the dominating factor in the determination of theresistance of a magnetic strip segment. In some embodiments, a contactarea on the arms of the spiral is placed such that each segment can haveapproximately the same resistance. However, due to process variations,there may be some variation in resistances among segments.

Furthermore, the resistance of each segment of the magnetic strip 101can vary with temperature. Some embodiments can implement resistancesensors that adjust for temperature fluctuations by measuringresistances and adjusting based on, for example, a temperature readingor a change in value of a reference element. In some embodiments, theresistances of the segments can be measured and decoded, accounting forvarying segment lengths and temperatures, to determine the state of themultiturn counter.

A comparator based sensor, such as shown in FIG. 7, can determine thestate of the magnetic strip in the presence of variations in temperaturewithout adjustments or additional temperature references. Furthermore,the comparator based sensor can be configured to compare neighboringsegments such that incremental segment length differences and/ordifferences in resistance due to process variations can have negligibleeffects in determining the state of the multiturn counter.

The examples shown in FIG. 1 and FIG. 2 depict a spiral shaped magneticstrip 101 as an open spiral based on a quadrilateral. However, in someother embodiments, different polygon or elliptical spiral configurationsare possible. Also, the spiral can be a closed spiral or a multi-layerspiral with overlapping parts.

FIG. 3 shows an example schematic diagram of a multiturn counter 300with a matrix of interconnects to a series of magnetoresistive elementsaccording to an embodiment. The illustrated multiturn counter 300includes matrix interconnections to magnetoresistive elements R1-R14.The magnetoresistive elements R1-R14 correspond to the magnetic stripsegments 103 a-103 n, respectively, of FIG. 1 in this example.Electrical connections are arranged in rows shown as Row1, Row2, Row3,and Row4. Electrical connections are arranged in columns shown as Col1,Col2, Col3, and Col4. The series connections of the magnetoresistiveelements R1-R14 indicated by the dashed lines corresponds to the seriesconnection of magnetoresistive elements R1-R14 in the schematicrepresentation 150 of FIG. 1. FIG. 3 also shows unused magnetoresistiveelements 317 and 319.

Together, the rows and columns form a matrix. The term “matrix” canrefer to a logical or functional organization (not necessarily ageometrical assignment and not necessarily a physical layout) ofelectrical connections to magnetoresistive elements. The labels “row”and “column” can be independent from orientation and can be reversible.Each illustrated magnetoresistive element R1-R14 has a first end and asecond end. In the embodiment shown in FIG. 3, rows of the matrixinclude electrical connections to first ends of magnetoresistiveelements, and columns of the matrix include electrical connections tosecond ends of magnetoresistive elements. The rows and columns shown inmatrix of FIG. 3 are not directly connected to each other. Instead, therows and columns can be electrically coupled to each other throughmagnetoresistive elements.

Row1 is electrically connected to first ends of magnetoresistiveelements R1, R2, R14, and R13. Row2 is electrically connected to firstends of magnetoresistive elements R4, R3, R11, and R12. Row3 iselectrically connected to first ends of magnetoresistive elements R5,R6, R10, and R9. Row4 is electrically connected to first ends ofmagnetoresistive elements R7 and R8.

Col1 is electrically connected to second ends of magnetoresistiveelements R1, R4, and R5. Col2 is electrically connected to second endsof magnetoresistive elements R2, R3, R6, and R7. Col3 is electricallyconnected to second ends of magnetoresistive elements R14, R11, and R10.Col4 is electrically connected to second ends of magnetoresistiveelements R13, R12, R9, and R8.

The magnetoresistive elements R1-R14 can have a variety of arrangementsin the matrix, and only one example embodiment is shown. In the exampleshown in FIG. 3, magnetoresistive elements 317 and 319 are unused andnot included as part of the series connection of magnetoresistiveelements. In some other embodiments, different magnetoresistive elementsof the illustrated arrangement can be used or unused.

As shown in FIG. 3, four columns and four rows of electrical connectionscan connect the 14 magnetoresistive elements in series with each other.Although a total of 28 schematic connection nodes are shown asconnecting the 14 magnetoresistive elements in FIG. 3, the schematicview shows the schematic connection nodes as duplicates of physicalconnection nodes for clarity. The connections can be implemented as 15physical connection nodes as shown in FIG. 4. More generally, fewerphysical connections than schematic connections can be implemented. Thiscan reduce parasitic effects and/or physical area of the circuit layout.

For “N” usable magnetoresistive elements arranged in series with eachother (i.e., 14 in FIG. 3), as few as “A” rows and “B” columns can beused where:

N≤A*B−A+2, where B is a positive even number, and

N≤A*(B−1)−A+3, where B is a positive odd number.

Accordingly, a relatively small number electrical connections can bemade between the magnetic strip and the matrix. This can simplify designand/or save on fabrication costs. In some embodiments, the number ofphysical connections between matrix and the magnetic strip is N+1 orN+2. In some embodiments, the number of physical connections between thematrix and the magnetic strip is less than 2N, or less than 2N+2, orless than 2N−2. As an approximation, the minimum number of rows andcolumns can increase with the square root of the number ofmagnetoresistive elements instead of increasing linearly with the numberof magnetoresistive elements.

In some embodiments, “N,” “A,” and “B,” can satisfy both of theequations, where K is a relatively small constant (e.g., ranging from 0to 3, inclusive):

N≤(A+K)*(B+K), and

N≥(A−K)*(B−K).

FIG. 4 shows an example layout 400 of the matrix from FIG. 3electrically connected to the magnetoresistive elements of the magneticstrip 101 from FIG. 1 according to an embodiment. As illustrated, themagnetic strip 101 of magnetoresistive elements R1 to R14 is physicallylaid out in the shape of a spiral. In FIG. 4, the rows Row1, Row2, Row3,and Row4 and columns Col1, Col2, Col3, and Col4 connect themagnetoresistive element segments R1-R14 as schematically shown in thematrix of FIG. 3. In FIG. 4, a total of 15 physical connection nodesbetween the magnetic strip 101 and the matrix interconnections areshown. For example, physical connection node 401 in FIG. 4 is theequivalent of schematic connection nodes 401 a, 401 b in FIG. 3 becausemagnetoresistive elements R1 and R2 are connected in series as part ofthe magnetic strip 101 at physical connection node 401. Examples ofphysical connection nodes between the matrix of interconnects and themagnetic strip can include, for example, an electrically conductiveconnection between the magnetic strip and a metal layer, a solderconnection to the magnetic strip, a via connection to the magneticstrip, a bump on the magnetic strip, a wire contact, etc.

In FIG. 4, the connections formed by the rows and columns can createshort circuits between different parts of the spiral. For example, aphysical connection node 401 between R1 and R2 is connected to a nodebetween R13 and R14. Accordingly, this can complicate the seriesconnection of magnetoresistive elements by creating a plurality ofparallel connections that can make it more difficult to measureresistances and decode the magnetic state of the circuit. In fact, thecomplexity of parallel connections can cause some previous sensordesigns can become inaccurate and/or inoperable to measure resistances.

A driving and sensing circuit (such as shown in FIG. 6, FIG. 7, and FIG.8) enables resistances to be determined despite the complexity ofadditional parallel connections. Such a driving and sensing circuit canbe used to read out the magnetic state stored by the magnetic strip 101and to provide an indication of a number of turns of a rotatable elementin located in proximity to the magnetic strip 101.

FIG. 5 shows a schematic diagram 500 of a matrix electrically connectedto a series of magnetoresistive elements for a 46 turn counter accordingto an embodiment. Columns A0-A13 and rows B0-B13 logically connect witha series of 184 magnetoresistive elements. The rows B0-B13 couple tofirst ends of magnetoresistive elements. The columns A0-A13 couple tosecond ends of magnetoresistive elements. The matrix has several unusedpositions. Various embodiments can have different matrix sizes, adifferent arrangement of the series of magnetoresistive elements,different locations for unused positions, etc. Accordingly, theprinciples and advantages discussed herein can be applied to matrices ofvarying sizes, varying numbers of magnetoresistive elements, and varyingarrangements of the series of magnetoresistive elements.

FIG. 6 shows an example schematic 600 of an electronic system thatincludes a driving and sensing circuit electrically connected through amatrix of interconnects to a series of magnetoresistive elements R1-R14according to an embodiment. The driving and sensing circuit comprises avoltage meter 601, current source 603, amplifier 605, column switches607, row switches 609, the matrix 300 electrically connected to theseries of magnetoresistive elements R1-R14 (e.g., as described inconnection with FIG. 3), and a reference node 613. The driving andsensing circuit can select a row and a column of the matrix 300 bycontrolling the column switches 607 and the row switches 609 to detect aresistance of a selected magnetoresistive element of themagnetoresistive elements R1-R14. Accordingly, the driving and sensingcircuit can read out an indication of the magnetic state stored by theselected magnetoresistive element. By taking at least twice as manyreadouts as the number of turns that can be counted by themagnetoresistive elements R1-R14, the number of turns (or a ratiothereof) of a rotatable element in located in proximity to themagnetoresistive elements R1-R14 can be determined. In some embodiments,the number of sensors can be relatively low (e.g., 1 or 2), even whencounting relatively high numbers of turns. Although more parallelsensors can be added for speed, using a relatively low number of sensorstypically reduces circuit complexity and production costs. A smallernumber of sensors can be used compared to other designs that involve anincreased number of sensors when the number of countable turnsincreases. The sensor can have outputs that are not tied together withreduced signal quality.

The driving circuit is configured to apply a current across the selectedmagnetoresistive element (e.g., magnetoresistive element R3 asillustrated in FIG. 6), thereby causing a voltage drop across theselected magnetoresistive element. The voltmeter 601 can detect and/ormeasure the voltage across the selected magnetoresistive element,thereby allowing a determination of the magnetic state (HR or LR) of asegment of the magnetic strip 101 (e.g., as explained in the discussionof FIG. 2). Any other suitable resistive sensing circuit arranged todetermine the resistive of the selected magnetoresistive element can beimplemented in place of or in addition to the voltmeter 601. Forexample, a comparator circuit can detect whether the magnetic state HRor LR is greater than or less than a medium resistance. Eachmagnetoresistive element can be individually selected and measured sothat the magnetic state of the multiturn sensor can be decoded todetermine how many times a magnetic field 201 has been fully rotatedaround the magnetoresistive elements R1-R14. In some embodiments, theguarding principle can be applied to enable sensing.

A magnetoresistive element of the magnetoresistive elements R1-R14 canbe selected by toggling a switch of the column switches 607 so that thecurrent source 603 is coupled to a single selected column (e.g., Col 2as illustrated in FIG. 6) in the matrix 300, the selected column havingan electrical connection to the selected magnetoresistive element (e.g.,R3 as illustrated in FIG. 6). The column switches 607 are configured toopen connections to unselected columns so that magnetoresistive elementselectrically coupled the unselected columns are electricallydisconnected from the voltmeter 601 and should not affect a voltagereading.

The current source 603 is input to an amplifier 605, such as a unitygain or an 1× amplifier, to cause the output of the amplifier 605 tohave approximately the same voltage as the voltage across the selectedmagnetoresistive element. Row switches 609 toggles to connect rows ofthe matrix to either the output of the amplifier 605 or the referencenode 613. The row switches 609 can be toggled such that a selected row(e.g., Row 2 as illustrated in FIG. 6), which is electrically connectedto the selected magnetoresistive element (e.g., R3 as illustrated inFIG. 6), is electrically connected to the reference node 613. As aresult, current provided through the selected column (e.g., Column 3 asillustrated in FIG. 6) can flow through the selected magnetoresistiveelement (e.g., R3) and flow through the selected matrix row (e.g., Row2) to the reference node 613. Rows not electrically connected to theselected magnetoresistive element can be electrically connected to theoutput of the amplifier 605 by way of the row switches 609. Accordingly,current (if any) provided through non-selected magnetoresistive elementsshould not cause a voltage drop across the non-selected magnetoresistiveelements.

Combinations of switches in the column switches 607 and combinations ofswitches in the row switches 609 can be toggled in a sequence such thatthe resistances of the different, individual segments of the magneticstrip 101 can be determined. Accordingly, the matrix can avoid tyingmultiple signals together and can avoid a reduced signal quality. Thecolumn switches 607 and the row switches 609 can be toggled by anysuitable control circuit (not illustrated in FIG. 6). The measuredvoltages can be sampled, held, stored, decoded, or any combinationthereof. Measured voltages can be converted to determine a resistance inaccordance with the equation V=I*R, and the resistances can be used todetermine the magnetic orientation the different segments of themagnetic strip 101 based on whether the resistance is high or low (e.g.,as described with reference to FIG. 2), and then a turn state can bedecoded. In some embodiments, additional circuitry, such as decoderlogic, a temperature varying reference component, or the like, canaccount for different segment lengths and/or temperature variations.

In some embodiments, the driving and sensing circuit can be suitablyadjusted to replace voltmeter 601 with an ohmmeter, ammeter, or othermeasurement circuit. In some embodiments, the current source 603 can bereplaced with a voltage source and the voltmeter 601 can be replacedwith an ammeter or other measurement device with minor adjustments tothe driving and sensing circuit of FIG. 6. In some embodiments, the rowswitches 609, column switches 607, and amplifier 605 can be duplicatedand/or coupled between the magnetoresistive elements and the matrix,thereby allowing another way to control connections between individualmagnetoresistive elements and the matrix. In some embodiments, thevoltmeter can be based on a Wheatstone bridge circuit, however, even insuch cases, the number of Wheatstone bridge circuits can reduced withouttying output signals together. In some embodiments, more than onematrix, one driving circuit, and one sensing circuit can be used. Forexample, two 2×4 matrixes, each with a driving and sensing circuit, canbe used where each matrix covers half of the 4×4 grid. This can allowparallel processing and faster speeds. In some embodiments, the rowswitches 609 and/or column switches 607 can be implemented astransistors, as mechanical switches, as microelectromechanical system(MEMS) switches, as a plurality of single switches, as single or multithrow switches, as single or multi pole switches, as changeoverswitches, various other switching technologies, or any combinationthereof.

A single sensing circuit (e.g., voltmeter 601) can be used regardless ofthe number of magnetoresistive elements in the matrix or the size of thematrix. Furthermore, the magnetoresistive elements electricallyconnected to the matrix are not wired as part of a Wheatstone bridgeconfiguration in the embodiment of FIG. 6. There are fewer outputs andless sensing circuitry in the embodiment of FIG. 6 compared to ifWheatstone bridge circuits were implemented.

FIG. 7 shows an example schematic 700 of a driving and sensing circuitelectrically connected through a matrix of interconnects to a series ofmagnetoresistive elements. Like in FIG. 6, the driving and sensingcircuit in FIG. 7 comprises a current source 603, amplifier 605, columnswitches 607, row switches 609, the matrix 300 electrically connected tothe series of magnetoresistive elements R1-R14 (as detailed in FIG. 3),a selected magnetoresistive element (e.g., R4 as illustrated in FIG. 7)at a selected column (e.g., Col1 as illustrated in FIG. 7) and aselected row (e.g., Row2 as illustrated in FIG. 7), and a reference node613. As shown in FIG. 7, the voltmeter 601 of FIG. 6 is replaced in FIG.7 with sample and hold (S&H) circuits 701, 703, a comparator 705, and adigitizer 707 such as an analog to digital converter or windowcomparator. The driving and sensing circuit can also include a node 709that, in some embodiments, can be an S&H selector such as a switch.

FIG. 7 shows a state where the column switches 607 and row switches 609are such that the driving and sensing circuit is configured to measure aresistance of the magnetoresistive element R4. The column switches 607in FIG. 7 has a different combination of opened and closed switchescompared to the column switches 607 in FIG. 6. This allows themeasurement to be made in connection with a different magnetoresistiveelement than in FIG. 6. The row switches 609 in FIG. 7 has the samecombination of opened and closed switches compared to the columnswitches 609 in FIG. 6, but it will be understood that the row switches609 in FIG. 7 can have a different combination of opened and closedswitches compared to the row switches 609 in FIG. 6 when selecting someother magnetoresistive elements. It will be further understood that thecolumn switches 607 and row switches 609 can select any one ofmagnetoresistive elements R1-R14 for measurement in either FIG. 6 orFIG. 7.

Selected magnetoresistive elements (e.g., R3 in FIG. 6 and R4 in FIG. 7)can be selected according to the principles explained above with respectto FIG. 6. Instead of measuring a voltage across the selectedmagnetoresistive elements and decoding the voltages, the voltages ofdifferent selected magnetoresistive elements are compared to each otherbefore decoding in the embodiment of FIG. 7.

The column switches 607 and row switches 609 can select amagnetoresistive element, the voltage across selected magnetoresistiveelement (e.g., R3) can be sampled and held by a first sample and holdcircuit 701. The column switches 607 and row switches 609 can selectanother magnetoresistive element, the voltage across othermagnetoresistive element (e.g., R4) can be sampled and held by a secondsample and hold circuit 703. An S&H selector can be used to togglebetween S&H circuit 701 and S&H circuit 703. The S&H selector can be,for example, a switch implemented at node 709 (not illustrated) toalternate between electrically coupling to S&H circuits 701, 703. Insome embodiments, both S&H circuits 701, 703 can be electricallyconnected at node 709, but a clock signal can be supplied to S&H circuit701 and an inverse clock signal can be supplied to S&H circuit 703.

In some embodiments, an analog comparison can be performed. A comparator705 can compare the outputs of S&H circuits 701 and 703. In someembodiments, digital components can be included with the analogcomponents. The output of the comparator 705 can be provided to thedigitizer 707 such as an analog to digital converter or windowcomparator. In some embodiments, the digitizer 707 includes a windowcomparator that has three outputs of high, zero, and low based onwhether a first input value is greater than, equal to, or less than asecond input value. The output of the digitizer can be stored,processed, or decoded.

In some embodiments, a digital comparison can be performed. An amplifiercan amplify a signal, such as a voltage, from row switches 607. Theamplifier can output an amplified analog signal to a digitizer. Thedigitizer can comprise an analog to digital converter or windowcomparator that converts the analog signal into a digital signal havinga digital value. The digital value can be stored into a memory and adigital processor such as a computer or decoder (for example, as shownin FIG. 8) configured as a comparator to compare the digital value toone or more other digital values. The output of the digitizer 707 can bestored, processed, or decoded. In some embodiments, a signal's value canbe stored in analog circuitry such as sample and hold circuits 701 and703, in a digital memory, or both.

The comparison process can be iterated to perform comparisons fordifferent combinations of magnetoresistive elements in a magnetic strip101. For instance, a comparison can be performed in connection with eachmagnetoresistive element of the magnetic strip 101. In some embodiments,each magnetoresistive element is compared to a neighboringmagnetoresistive element (e.g., R1 is compared to R2, R2 is compared toR3, R3 is compared to R4, etc.). In some embodiments, eachmagnetoresistive element in the magnetic strip 101 can be compared atleast once. In some embodiments, the magnetoresistive elements are notcompared to neighboring magnetoresistive elements. In some embodiments,the comparisons can be performed in a different order. In someembodiments, only a sufficient comparison of magnetoresistive elementsto generate unique comparisons of outputs performed. The comparisonoutputs can be decoded to determine the state of the multiturn counter.The comparison sensors system can be used where relatively largetemperature variations might occur (e.g., in a vehicle, outdoors)because temperature changes may affect all magnetoresistive elementssubstantially equally or proportionally. Accordingly, by comparingmagnetoresistive elements, temperature variations can be canceled out,at least in part, to have reduced, minimal or even no impact onaccuracy.

FIG. 8 shows an example multiturn counter system 800 according to anembodiment. The system includes a rotatable object 801, axles 803 and807, gears 805, one or more magnets 811, a magnetic field 201, a domainwall generator 107, a magnetic strip 101, an interconnect matrix 300,column switches 607, row switches 609, a driving circuit 815, a sensingcircuit 817, a control circuit 819, an angle sensor system 821, acomputing device 829, a CPU or decoder 823, memory 825, and an outputport 827. The driving circuit 815 and sensing circuit 817 can implementany of the principles and advantages described in connection with thedriving and sensing circuits discussed herein, for example, withreference to FIG. 6 and/or FIG. 7.

A rotatable object, such as a knob, a steering wheel, a lever, a handle,a propeller, a wheel, a ball, etc. can be coupled to the magnet 811. Oneor more axels 803, 807 and gears 805 can be used to multiply the numberof times that the magnet 811 rotates per turn of the object 801. Whileaxels and gears are illustrated in FIG. 8, it will be understood thatneither axels nor gears are included in certain embodiments. The magnet811 generates a magnetic field 201 and causes the magnetic field 201 toorient in different directions based on the orientation of the magnet.Changing the magnetic field 201 can cause a domain wall generator 107 topropagate domain walls through a magnetic strip 101, which can bephysically laid out in the shape of a spiral. Switches 607 and 609,which can be toggled in particular sequences by a control circuit 819,can couple a driving circuit 815 and sensing circuit 817 through aninterconnect matrix 300 to the magnetic strip 101. Measurements of thesensing circuit can be provided (e.g., transmitted) to a computer 829.The measurements can be stored in a memory 825, and a CPU or decoder 823can convert the measurements into a decoded output, which can be adigital output, to be output through output port 827 or to be usedinternally within the computing device (e.g., within CPU 823). Thesystem 800 can include an angle sensor system 821. An angle sensorsystem can detect an angular position of the turning object 801, but maylack the ability to count turns (e.g., be unable to differentiatebetween zero degrees and 360 degrees). The angle sensor can be, forexample, a single or half turn angle sensor. The angle sensor can bebased on anisotropic magnetoresistive, tunnel magnetoresistance, GMR,Hall effect, or other technology. The decoded output 827 can be used inconjunction with the angle sensor system 821 to precisely determineaccumulated turned angle of the object 801.

FIGS. 9-18 show an example of progressive turn states of an example 2turn counter. Although a 2 turn sensor is shown for illustrativepurposes, the principles and advantages discussed with reference tothese figures can be applied to other multiturn sensors. Additionally,these features discussed with respect to FIG. 9-18 can be implementedwith any of the other principles and advantages discussed herein.

FIG. 9 shows a multiturn sensing system 900, magnetic strip 901, domainwall generator 107, magnetic field 201, output graph 903 correspondingto a turn angle of zero degrees, and comparison outputs 907, 909, 911,913, 915, 917, and 919. FIGS. 10-18 also show domain walls 921, 923,925, 927, 929.

The magnetic strip 901 is laid out in the physical shape of a spiral,having rounded corners and straight segments. The magnetic strip 901 iscoupled to a DWG 107 configured to propagate domain walls through themagnetic strip 901, thereby changing magnetic orientations of parts ofthe magnetic strip.

The straight segments function as variable magnetoresistive elements R1to R8 that can have a high resistance value “H” or low resistance value“L” depending on the magnetic domain within the segment. Themagnetoresistive element states shown for the spiral 901 can be used todecode a sequence of measured resistances (e.g., the outputs of circuit600 in FIG. 6) into a turn state. End magnetoresistive elements R0 andR9 are unused, although in other embodiments, R0 and R9 can be used.

Signals corresponding to the output graph 903 can be used to decode thecompared outputs of magnetoresistive elements, for example, the outputsfrom the circuit 700 in FIG. 7. Depending on the specificimplementations details of FIG. 7, graph 903 can correspond to aninverted output. Output graph 903 shows output 907 of the resistance ofR1 compared to the resistance of R2, output 909 of the resistance of R2compared to the resistance of R3, output 911 of the resistance of R3compared to the resistance of R4, output 913 of the resistance of R4compared to the resistance of R5, output 915 of the resistance of R5compared to R6, output 917 of the resistance of R6 compared to R7, andoutput 919 of the resistance of R7 compared to the resistance of R8. Thecomparison outputs can be low (first magnetoresistive element has alower resistance than the second magnetoresistive element), zero(magnetoresistive elements have equal resistances), or high (firstmagnetoresistive element has a higher resistance than the secondmagnetoresistive element).

FIG. 10 shows the example 2 turn counter of FIG. 9 in a starting stateat 0 degrees. A first domain wall 921 is generated by the domain wallgenerator in response to a rotation in the magnetic field 201. In FIG.10, magnetoresistive elements R1, R5, R9, R4, and R8 have lowresistances and magnetoresistive elements R2, R6, R3, and R7 have highresistances. As shown by the output graph 903, output 907 of R1:R2 islow, output 909 of R2:R3 is zero, output 911 of R3:R4 is high, output913 of R4:R5 is zero, output 915 of R5:R6 is low, output 917 of R6:R7 iszero, and output 919 of R7:R8 is high.

FIG. 11 shows the example 2 turn counter of FIG. 9 in a state where themagnetic field has rotated clockwise 90 degrees relative to the statecorresponding to FIG. 10. In FIG. 11, the first domain wall 921 isshifted past R1. In FIG. 11, magnetoresistive elements R5, R9, R4, andR8 have low resistances and magnetoresistive elements R1, R2, R6, R3,and R7 have high resistances. As shown by output graph 903, output 907of R1:R2 is zero, output 909 of R2:R3 is zero, output 911 of R3:R4 ishigh, output 913 of R4:R5 is zero, output 915 of R5:R6 is low, output917 of R6:R7 is zero, and output 919 of R7:R8 is high.

FIG. 12 shows the example 2 turn counter of FIG. 9 in a state where themagnetic field has rotated clockwise 180 degrees relative to the statecorresponding to FIG. 10. In FIG. 12, the first domain wall 921 isshifted past R2, and a second domain wall 923 is generated. In FIG. 12,magnetoresistive elements R2, R5, R9, R4, and R8 have low resistances,and magnetoresistive elements R1, R6, R3, and R7 have high resistances.As shown by output graph 903, output 907 of R1:R2 is high, output 909 ofR2:R3 is low, output 911 of R3:R4 is high, output 913 of R4:R5 is zero,output 915 of R5:R6 is low, output 917 of R6:R7 is zero, and output 919of R7:R8 is high.

FIG. 13 shows the example 2 turn counter of FIG. 9 in a state where themagnetic field has rotated clockwise 270 degrees relative to the statecorresponding to FIG. 10. In FIG. 13, the first domain wall 921 isshifted past R3 in FIG. 13, and a second domain wall 923 is shifted pastR1. In FIG. 13, magnetoresistive elements R1, R2, R3, R5, R4, and R8have low resistances, and magnetoresistive elements R6 and R7 have highresistances. As shown by output graph 903, output 907 of R1:R2 is zero,output 909 of R2:R3 is zero, output 911 of R3:R4 is zero, output 913 ofR4:R5 is zero, output 915 of R5:R6 is low, output 917 of R6:R7 is zero,and output 919 of R7:R8 is high.

In some embodiments, due to the longer length of R3 compared to R1, thedomain wall 921 may take longer to shift past R3 than the time it takesfor domain wall 923 to shift past R1. This can be accounted for byincreasing a clock duty cycle to have a period long enough for a domainwall to pass the longest segment of the magnetic strip 901 beforesensing a measurement. Alternatively, a decoder can be implemented toaccount for the timing glitches because the outputs nonetheless canproduce unique, decodable combinations despite the different timings.

FIG. 14 shows the example 2 turn counter of FIG. 9 in a state where themagnetic field has rotated clockwise 360 degrees relative to the statecorresponding to FIG. 10. In FIG. 14, the first domain wall 921 isshifted past R4, the second domain wall 923 is shifted past R2, and athird domain wall 925 is generated. In FIG. 14, magnetoresistiveelements R1, R3, R5, and R8 have low resistances, and magnetoresistiveelements R2, R4, R6, and R7 have high resistances. As shown by outputgraph 903, output 907 of R1:R2 is low, output 909 of R2:R3 is high,output 911 of R3:R4 is low, output 913 of R4:R5 is high, output 915 ofR5:R6 is low, output 917 of R6:R7 is zero, and output 919 of R7:R8 ishigh.

FIG. 15 shows the example 2 turn counter of FIG. 9 in a state where themagnetic field has rotated clockwise 450 degrees relative to the statecorresponding to FIG. 10. In FIG. 15, the first domain wall 921 isshifted past R5, the second domain wall 923 is shifted past R3, and thethird domain wall 925 is shifted past R1. In FIG. 15, magnetoresistiveelement R8 has a low resistance, and magnetoresistive elements R1, R2,R3, R4, R5, R6, and R7 have high resistances. As shown by output graph903, output 907 of R1:R2 is zero, output 909 of R2:R3 is zero, output911 of R3:R4 is zero, output 913 of R4:R5 is zero, output 915 of R5:R6is zero, output 917 of R6:R7 is zero, and output 919 of R7:R8 is high.

FIG. 16 shows the example 2 turn counter of FIG. 9 in a state where themagnetic field has rotated clockwise 540 degrees relative to the statecorresponding to FIG. 10. In FIG. 16, the first domain wall 921 isshifted past R6, the second domain wall 923 is shifted past R4, thethird domain wall 925 is shifted past R2, and a fourth domain wall 927is generated. In FIG. 16, magnetoresistive elements R2, R4, R6, and R8have low resistances, and magnetoresistive elements R1, R3, R5, and R7have high resistances. As shown by output graph 903, output 907 of R1:R2is high, output 909 of R2:R3 is low, output 911 of R3:R4 is high, output913 of R4:R5 is low, output 915 of R5:R6 is high, output 917 of R6:R7 islow, and output 919 of R7:R8 is high.

FIG. 17 shows the example 2 turn counter of FIG. 9 in a state where themagnetic field has rotated clockwise 630 degrees relative to the statecorresponding to FIG. 10. In FIG. 17, the first domain wall 921 isshifted past R7, the second domain wall 923 is shifted past R5, thethird domain wall 925 is shifted past R3, and the fourth domain wall 927is shifted past R1. In FIG. 17, magnetoresistive elements R1-R8 have lowresistances. All outputs 907, 909, 911, 913, 915, 917, and 919 are zero.

FIG. 18 shows the example 2 turn counter of FIG. 9 in a state where themagnetic field has rotated clockwise 720 degrees (2 turns) relative tothe state corresponding to FIG. 10. In FIG. 18, the first domain wall921 is shifted past R8, the second domain wall 923 is shifted past R6,the third domain wall 925 is shifted past R4, the fourth domain wall 927is shifted past R2, and a fifth domain wall 929 is generated. In FIG.18, magnetoresistive elements R1, R5, R3, and R7 have low resistances,and magnetoresistive elements R2, R4, R6, and R8 have high resistances.As shown by output graph 903, output 907 of R1:R2 is low, output 909 ofR2:R3 is high, output 911 of R3:R4 is low, output 913 of R4:R5 is high,output 915 of R5:R6 is low, output 917 of R6:R7 is high, and output 919of R7:R8 is low. Additional clockwise rotations (beyond 2 turns) could,in some embodiments, cause an overdrive situation where the outputswould no longer be unique.

The outputs shown in FIGS. 9-18 show unique output combinations for eachconsecutive 90 clockwise turn. In addition to detecting turns in asingle direction, the multiturn sensor can detect bidirectionalrotations in the magnetic field with 180 degree accuracy, for example,as illustrated below with respect to FIG. 19 and FIG. 20. The outputgraph can be decoded to reflect the accumulated number of bidirectionalrotations.

FIG. 19 shows the example 2 turn counter in a state where the magneticfield has rotated counterclockwise 90 degrees relative to the statecorresponding to FIG. 15 to have an accumulated rotation of 360 degreesrelative to the state corresponding to FIG. 10. The state of the domainwalls, magnetoresistive element resistance, and compared outputs are thesame as described for FIG. 15.

FIG. 20 shows the example 2 turn counter in a state where the magneticfield has rotated counterclockwise 90 degrees relatively to the statecorresponding to FIG. 19 to have an accumulated rotation of 270 degreesrelative to the state corresponding to FIG. 10. In FIG. 20, the firstdomain wall 921 is shifted between R4 and R5, the second domain wall 923is shifted between R2 and R3, and the third domain wall 925 shiftedbetween R1 and the DWG 107. In FIG. 20, magnetoresistive elements R1,R3, R5, and R8 have low resistances, and magnetoresistive elements R2,R4, R6, and R7 have high resistances. As shown by output graph 903,output 907 of R1:R2 is low, output 909 of R2:R3 is high, output 911 ofR3:R4 is low, output 913 of R4:R5 is high, output 915 of R5:R6 is low,output 917 of R6:R7 is zero, and output 919 of R7:R8 is high.

FIG. 19 and FIG. 20 show that a 180 degree resolution is achieved whenreversing directions. Accordingly, as shown by the examples in FIG. 19and FIG. 20, the multiturn sensor can achieve a 180 degree resolution inuse in both the clockwise and counterclockwise directions.

FIG. 21 shows an example method 2100 for reading a state of a giantmagnetoresistance sensor. The method can be used to sequentially select,power, and measure individual segments in a GMR sensor to determine anaccumulated turn state. The method can be implemented, for example,using the circuits shown in FIG. 6 and in FIG. 7.

At block 2101, a first sequence of rows in a matrix is powered, the rowsbeing coupled to a magnetic strip of a plurality of magnetoresistiveelements. Powering can include providing a voltage, current (e.g.,current source 603 in FIG. 6 and in FIG. 7), or a reference value. Afirst example of a sequence for four rows of switches ABCD (e.g., rowswitches 609 in FIGS. 6 and 609 in FIG. 7) includes [0111, 0111, 1011,1011, 1101, 1101, 1110, 1110, 1101, 1101, 1011, 1011, 0111, 0111] where0 represents a first switch state and 1 represents a second switchstate. The first switch state can cause the switch to electricallycouple to a grounding or reference voltage. The second switch state cancause the switch to electrically couple to a different circuit pathway,such as to output of amplifier 605 of FIG. 6 and FIG. 7. Other examplesof sequences include parts of the first example, reordered permutationsof the first example, the first example with inverted values, the firstexample with more or fewer combinations in the sequence, and the secondexample with different values.

At block 2103, a second sequence of columns in a matrix is powered, thecolumns being coupled to the magnetic strip of the plurality ofmagnetoresistive elements. A second example of a sequence for fourcolumns WXYZ (e.g., column switches 607 in FIGS. 6 and 607 in FIG. 7)includes [1000, 0100, 0100, 1000, 1000, 0100, 0100, 0001, 0001, 0010,0010, 0001, 0001, 0010] where 0 represents an open switch and 1represents a closed switch. Other examples of sequences include parts ofthe second example, reordered permutations of the second example, thesecond example with inverted values, the second example with more orfewer combinations in the sequence, and the second example withdifferent values.

At block 2105, a sequence of electromagnetic properties ofmagnetoresistive elements of the plurality of magnetoresistive elementsis sensed. The electromagnetic properties can be indicative ofresistance. In some embodiments, the first sequence and the secondsequence are such that a sensing circuit is configured to make ameasurement of a sequence of individual, selected magnetoresistiveelements. In some embodiments, sequence of individual, selectedmagnetoresistive elements are the sequence of magnetoresistive elementsin the magnetic strip as arranged in the magnetic strip. In someembodiments, the sequence of individual, selected magnetoresistiveelements include the magnetoresistive elements in the magnetic strip sothat a unique output is made for 180 turn resolutions. In someembodiments, electromagnetic properties can be a resistance, a voltage,a current, or a comparison of a resistance, voltage, or current. In someembodiments, the electromagnetic properties can be sensed by avoltmeter, ammeter, ohmmeter, sample and hold circuit, comparator, oranalog to digital converter.

At block 2107, the sensed sequence of electromagnetic properties isdecoded to determine an accumulated turn state. The decoding can be donefor example, by using a lookup table of magnetoresistive element valuesand corresponding turn states. As another example, a combination of turnstates (e.g., as shown in the output graphs 903 of FIGS. 9-20) can beused to identify the accumulated turn state with 90 degree accuracy inone direction or 180 degree accuracy in two directions.

FIG. 22 shows an example method 2200 for making a multiturn sensor, forexample, any of the multiturn sensors and parts thereof as shown inFIGS. 1-8.

At block 2201, a magnetic strip is formed in the shape of spiral, forexample, as shown in FIG. 1, FIG. 2, and FIG. 4. The spiral can havestraight segments and rounded corners, and the segments can have amagnetically variable resistance as domain walls propagate through thesegments.

At block 2203, a domain wall generator (such as domain wall generator107 of FIG. 1) can be coupled to one end of the spiral. This can be partof the same processing step as forming the magnetic strip in certainembodiments.

At block 2205, nodes of the magnetic strip can be shorted with a matrixof interconnections, for example, as shown in FIG. 3 and in FIG. 4. Insome embodiments, the nodes can be coupled to the rounded cornersbetween the straight segments. The matrix can have rows and columns,wherein rows connect to first ends of the straight segments and whereinthe columns connect to second ends of the straight segments.

At block 2207, the matrix of interconnections can be coupled to adriving circuit, such as driving circuit 815 of FIG. 8. The drivingcircuit can couple to at least one of the rows and columns of thematrix. The driving circuit can include, for example, the current source603 and amplifier 605 of FIG. 6 and FIG. 7.

At block 2209, the matrix of interconnections can be coupled to asensing circuit. The sensing circuit can include, for example, thevoltmeter 601 of FIG. 6. The sensing circuit can include, for example,the sample and hold circuits 701, 703 and the digitizer circuit 707 ofFIG. 7. In some embodiments, additional components, such as those shownin FIG. 8, can be further coupled to the multiturn sensor.

The various features and processes described above may be implementedindependently of one another, or may be combined in various ways. Allpossible combinations and subcombinations are intended to fall withinthe scope of this disclosure. In addition, certain method or processblocks may be omitted in some implementations. The methods and processesdescribed herein are also not limited to any particular sequence, andthe blocks or states relating thereto can be performed in othersequences that are appropriate. For example, described blocks or statesmay be performed in an order other than that specifically disclosed, ormultiple blocks or states may be combined in a single block or state.The example blocks or states may be performed in serial, in parallel, orin some other manner. For example, forming a magnetic strip in the shapeof a spiral in block 2201 and coupling a domain wall generator to oneend of the spiral in block 2203 can be performed in parallel during thesame fabrication step. Blocks or states may be added to or removed fromthe disclosed example embodiments. The example systems and componentsdescribed herein may be configured differently than described. Forexample, elements may be added to, removed from, or rearranged comparedto the disclosed example embodiments. Various embodiments can applydifferent techniques for fabricating different types of electronicdevices. Some embodiments apply to the fabrication of giantmagnetoresistance sensors.

In the embodiments described above, apparatuses, systems, and methodsfor multiturn sensors are described in connection with particularembodiments. It will be understood, however, that the principles andadvantages of the embodiments can be used for any other systems,apparatus, or methods that could benefit from a multiturn magneticsensor. Although certain embodiments are described with reference toparticular spiral shapes, a 2 turn sensor, particular types of magneticproperties, particular matrix dimensions, it will be understood that theprinciples and advantages described herein can be applied to a varietyof applications using different spiral shapes, sensors capable ofcounting a different number of turns or partial turns, different typesof magnetic properties, different matrix sizes (e.g., minimum of 3×3,minimum of 2×3, minimum of 3×2, minimum of 3×4, and larger). In certainembodiments, the spiral can have a minimum number of magnetoresistiveelements, such as 3, 4, 5, 6, 7, 8, 9, or more. Although certainembodiments are described with reference to a circuit that includes asingle driving circuit and a single sensing circuit, in someembodiments, multiple sensing circuits and driving circuits can operatethrough multiple matrixes on different parts of a spiral in parallel tomore quickly decode the accumulated turn state. Moreover, while somecircuit schematics are provided for illustrative purposes, otherequivalent circuits can alternatively be implemented to achieve thefunctionality described herein.

The principles and advantages described herein can be implemented invarious apparatuses. Examples of such apparatuses can include, but arenot limited to, vehicles, motors, treadmills, flywheels, GPS systems,gates, population counters, consumer electronic products, parts of theconsumer electronic products, electronic test equipment, etc. Consumerelectronic products can include, but are not limited to, wirelessdevices, a mobile phone (for example, a smart phone), healthcaremonitoring devices, vehicular electronics systems such as automotiveelectronics systems, a computer, a hand-held computer, a tabletcomputer, a laptop computer, a personal digital assistant (PDA), amicrowave, a refrigerator, a stereo system, a cassette recorder orplayer, a DVD player, a CD player, a digital video recorder (DVR), aVCR, a radio, a camcorder, a camera, a digital camera, a washer, adryer, a washer/dryer, a copier, a facsimile machine, a scanner, amulti-functional peripheral device, a wrist watch, a clock, etc. Otherapparatuses include anything with a movable or rotatable part where theamount of movement is measured. Further, apparatuses can includeunfinished products.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,”“include,” “including,” and the like are to be construed in an inclusivesense, as opposed to an exclusive or exhaustive sense; that is to say,the words should be construed in the sense of “including, but notlimited to.” The words “coupled” or “connected”, as generally usedherein, refer to two or more elements that can be either directlyconnected, or connected by way of one or more intermediate elements.Additionally, the words “herein,” “above,” “below,” and words of similarimport, if and when used in this application, shall refer to thisapplication as a whole and not to any particular portions of thisapplication. Where the context permits, words in the DetailedDescription using the singular or plural number can also include theplural or singular number, respectively. The words “or” in reference toa list of two or more items, is intended to cover all of the followinginterpretations of the word: any of the items in the list, all of theitems in the list, and any combination of the items in the list. Allnumerical values provided herein are intended to include similar valueswithin a measurement error.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states.

The teachings of the inventions provided herein can be applied to othersystems, not necessarily the systems described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein can be embodied in a variety of otherforms. Furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein can be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure. Accordingly,the scope of the present inventions is defined by reference to theclaims.

1. A system comprising: a multiturn counter configured to store amagnetic state associated with a number of accumulated turns of amagnetic field, the multiturn counter configured to count at least twoturns, and the multiturn counter comprising: a plurality ofmagnetoresistive elements electrically coupled in series with eachother, the plurality of magnetoresistive elements comprising at leasteight magnetoresistive elements; and a matrix of electrical connectionsarranged to electrically connect magnetoresistive elements of theplurality of magnetoresistive elements to other magnetoresistiveelements of the plurality of magnetoresistive elements, the matrix beingat least three by three.
 2. The system of claim 1, further comprising adriving and sensing circuit configured to select an individualmagnetoresistive element of the plurality of magnetoresistive elementsand to determine a measure of resistance of the individualmagnetoresistive element.
 3. The system of claim 2, further comprising adecoder configured to provide an output indicative of the number ofaccumulated turns of the magnetic field based the measure of resistanceof the individual magnetoresistive element and respective measures ofresistance of other magnetoresistive elements of the plurality ofmagnetoresistive elements.
 4. The system of claim 1, wherein theplurality of magnetoresistive elements are part of a magnetic strip thatis physically laid out in a spiral shape.
 5. The system of claim 1,wherein the multiturn counter further comprises a domain wall generatorcoupled to one end of the plurality of magnetoresistive elements.
 6. Thesystem of claim 1, wherein the multiturn counter is configured to countN turns, the system further comprising: a number of sensing circuits,the number being less than 2 times N; and a plurality of switchesconfigured to electrically couple the individual magnetoresistiveelement to an individual sensing circuit of the number of sensingcircuits.
 7. The system of claim 1, wherein: the spiral has Nmagnetoresistive elements, where N is greater than or equal to 8; thespiral has R physical connections to rows of electrical connections ofthe matrix of electrical connections; the spiral has C physicalconnections to columns of electrical connections of the matrix ofelectrical connections; the following equations are satisfied:N≤(R+1)*(C+1); andN≥(R−1)*(C−1); C is 3 or greater; and R is 3 or greater.
 8. A systemwith multiturn magnetic sensing, the system comprising: a stripcomprising a plurality of magnetoresistive elements electrically coupledin series with each other, the plurality of magnetoresistive elementstogether configured to store a state associated with an accumulatednumber of turns of a magnetic field; and a driving and sensing circuitcoupled to the strip, the driving and sensing circuit configured toselect an individual magnetoresistive element of the plurality ofmagnetoresistive elements to cause a voltage drop across the individualmagnetoresistive sensing element, and the driving and sensing circuitconfigured to provide an indication of a resistance of the individualmagnetoresistive element.
 9. The system of claim 8, further comprising amatrix of electrical connections coupled to a plurality of nodes on thestrip, wherein the driving and sensing circuit is coupled to the stripvia the matrix of electrical connections.
 10. The system of claim 9,wherein the matrix comprises rows of electrical connections and columnsof electrical connections, and the driving and sensing circuit isconfigured select a row of the rows and a column of the columns toselect the individual magnetoresistive sensing element.
 11. The systemof claim 9, wherein the matrix electrically connects magnetoresistiveelements of the plurality of magnetoresistive elements to respectiveother magnetoresistive elements of the plurality of magnetoresistiveelements.
 12. The system of claim 8, further comprising a domain wallgenerator configured to propagate one or more domain walls through thestrip in response to a rotation of the magnetic field.
 13. The system ofclaim 8, wherein the plurality of magnetoresistive elements compriseeight magnetoresistive elements.
 14. The system of claim 8, wherein thestrip has a spiral shaped layout.
 15. The system of claim 8, furthercomprising a decoder electrically connected to the driving and sensingcircuit, the decoder configured to determine the state associated withthe accumulated number of turns of the magnetic field and to provide anoutput indicative of the number of accumulated turns of the magneticfield.
 16. The system of claim 8, wherein the driving and sensingcircuit is configured to select different individual magnetoresistiveelements from the plurality of magnetoresistive elements and todetermine an indication of resistance of each of the different theindividual magnetoresistive elements.
 17. A method of multiturn magneticsensing, the method comprising: storing, with a strip comprising aplurality of magnetoresistive elements electrically connected in serieswith each other, a state associated with an accumulated number of turnsof a magnetic field; selecting an individual magnetoresistive element ofthe plurality of magnetoresistive elements to cause a voltage dropacross the individual magnetoresistive element; and detecting a measureof resistance of the individual magnetic magnetoresistive element. 18.The method of claim 17, wherein said selecting comprises selecting a rowof a plurality of rows of a matrix of electrical connections and acolumn of a plurality of columns of the matrix of electricalconnections, wherein the matrix of electrical connections is coupled toa plurality of nodes on the strip.
 19. The method of claim 17, furthercomprising determining, with a decoder, the state associated with theaccumulated number of turns of the magnetic field based at least partlyon said detecting.
 20. The method of claim 17, further comprising:selecting a different individual magnetoresistive element from theplurality of magnetoresistive elements to cause a voltage drop acrossthe different individual magnetoresistive element; and detecting ameasure of resistance of the different individual magneticmagnetoresistive element.